Alternate wetting and drying water management can reduce phosphorus availability under lowland rice cultivation irrespective of nitrogen level.

The limited availability of phosphorus (P) in the soil, which is affected by soil moisture, has a significant impact on crop production. However, we still do not fully understand how water management and nitrogen (N) addition affect the availability of P in paddy soil. An evaluation of the effects of two water management strategies that is continuous flooding (CF) and alternate wetting and drying (AWD) irrigation along with various nitrogenous fertilizer addition rates (equivalent to 0, 100%, 133%, and 166% recommended dose of N addition) on P availability in paddy soil took place over the course of a 2-year field experiment. The results showed that water management had a significant influence on ferrous iron, microbial biomass P, and soil-available P. However, the addition of N did not affect the availability of P in the soil. When N was added at various rates, AWD consistently reduced the amount of soil-available P compared to CF. This was primarily because AWD increased microbial biomass, which immobilized P and decreased the content of ferrous iron. As a result, the soil's ability to absorb P increased, leading to a decrease in the amount of P available. In conclusion, AWD decreases the amount of available P in paddy soil compared to CF.

Sustainable agriwaste management at farm level through self-reliant farming system.

Annually 500 M t organic wastes are produced in India from the agriculture sector. Transportation of bulky organic manures for centralized collection, processing and distribution to farms is cost prohibitive. Hence, recycling of agricultural wastes using vermicompost technology at the farm level is a practical way of managing agriwaste for meeting the plant nutrient requirement. Our experience with a 1.584 ha farm for three years (2015-2016 to 2017-2018) revealed that 8.1 t vermicompost was produced in three batches from 24 t agriwastes produced within the farm area. The system productivity by recycling these farm generated agriwastes and run-off water was 18.05 t (≈11.4 t ha-1) rice equivalent yield which was higher by 2.6 times as compared to rice fallow (4.46 t ha-1). Also, the net return from this system (Indian rupees 70141 ha-1) was higher by 2.3 times, after considering the fixed cost towards construction of a water recycling pond. An increase in carbon stock in soil for the four years study period was 0.66 Mg ha-1 year-1 with the agriwaste recycling system under organic nutrition. For the inorganic fertilizer plot, the increase in carbon stock was 0.53 Mg ha-1 year-1. A decrease in bulk density from 1.56 to 1.46 Mg m-3, increase in water holding capacity from 0.43 to 0.52 cm3 cm-3 and increase in available P and K content in soil from 38.0 and 174.7 kg ha-1 to 45.8 and 186.5 kg ha-1, respectively, were noted. Thus, recycling of agricultural waste at the farm level is useful in improving soil health and crop productivity.